Well, that's the question - is Eve allowed to forward packets, in the act of listening, or is that the Mallory's job? I don't know.
You can't measure a single-particle state without at least some chance of destroying the state. (Even quantum non-demolition methods affect the measured system a bit.) So you can't have a purely passive Eve. Perhaps "Quentin" is the Quantum Eavesdropper who makes his optimal tradeoff between gathering the most information and being the least detectable.
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